Motor-vehicle crashes are recognized as a major public health problem posing a significant threat across the age spectrum. To address this problem the National Highway and Transportation Safety Administration ("NHTSA") has promulgated standards for vehicle occupant protection. Federal Motor Vehicle Safety Standard (FMVSS) 208, 209, and 210 set the requirements for occupant restraints and FMVSS 213 sets standards for child restraint systems used in motor vehicles. State laws have supported NHTSA's efforts in that all 50 states now require the use of child restraints for infants and young children. Automobile manufacturers have augmented NHTSA's efforts by installing 3-point restraint systems in the front and rear outboard seating positions in all American made cars. Notwithstanding these improvements, motor-vehicle crashes are still one of the highest preventable causes of death and injury to our nation's children.
Five-to-seven year old children are a special group with respect to motor vehicle occupant restraints. Having outgrown child safety seats specifically designed for young children, they must now use the seatbelt systems designed for the adult body configuration. The 3-point restraint system, however, was not designed for a mid-size child. A Type II seatbelt assembly is designed to fit occupants whose weight and dimensions range from those of a 5th-percentile adult female to those of a 95th-percentile adult male (FMVSS 209).
The conventional lap belt is designed to restrain the adult body just below its center of gravity through the antero-superior iliac crests. However, the anterior iliac crests of a child are smaller and not developed to serve as anchor points. Consequently the belt can ride up over the abdomen allowing for submarining, thus causing injury to the intra-abdominal organs. The fitment of the shoulder belt also presents a problem in that it tends to lie anywhere from very high on the child's neck to across the face. This not only impedes the child's view, but is distinctly uncomfortable and more importantly, it loads the neck.
The conventional 3-point restraint system uses a single length of webbing to provide both lap and shoulder restraint. It passes from a floor-mounted retractor attached to the automobile up to a fitting on the B-pillar, then down across the shoulder to a slip-joint on the buckle connector, and from there back across the lap to an outboard floor attachment (FMVSS 209). The slip-joint allows slack created in the retractor-mounted shoulder belt to transfer to the lap belt, thus altering the lap belt's fit.
The behavioral characteristics of young children can influence the protective effect of the adult 3-point restraint system, i.e., the child may lean forward, fidget about, kneel in order to see out, or engage in other activities that compromise the fitment of the belt system. Additionally, medical experts agree that the anatomical characteristics of the child prevent optimum protection.
Although experts agree that belts can afford protection for young children, they warn against the risk of injury when used alone and recommend that belts be used in conjunction with a booster seat. A booster seat is a device consisting of only a seating platform that does not extend up to provide a cushion for the child's back or head (FMVSS 213). The manufacturers of booster seats on the market today have opted to leave off a backrest on these devices because there is no means yet available, prior to the present invention, to prevent a backrest from traveling forward on impact and generating secondary loading onto the child. Such results, as determined by a dynamic sled test, are prohibited by FMVSS 213.
Booster seats are designed to restrain the child and the booster seat by either of two methods: (a) A fixed or removable shield restrains the child's torso and pelvis while the device itself is restrained by routing the lap belt around the outer circumference of the shield; (b) Lap belt guides on each side of the booster seat serve to retain the device and to position the lap belt across the child's pelvis; the torso is restrained by the shoulder belt.
Booster seats have many disadvantages. Primarily, it is difficult to restrain the child in the booster seat and, at the same time, properly secure the booster seat to the automobile seat so that, in the event of a sudden stop, the booster seat and the child are both properly restrained without injury to the child. Inherent shoulder belt slack can transfer via the slip-joint to the lap belt, thus compromising the fitment of the seatbelt system. A snugly fitting shield is inconvenient for the child and, alternatively, if left fitting loosely, allows the child to build up momentum during an accident prior to contact with the shield. The lack of a backrest on the booster seat precludes proper positioning of the shoulder belt. The child's back is supported only by the automobile seat back which provides neither lateral nor neck support. For these and other reasons, booster seats for mid-size children have a low usage rate.
Adding a backrest to a booster seat can enhance the child's comfort and can provide lateral and neck support. The backrest also acts as a guide for the shoulder belt. Testing of a seat having a backrest, however, revealed that, upon impact or sudden deceleration of the automobile, the back of the seat travels forward and applies additional impact forces upon the child.